Host processor systems may store and retrieve data using a storage device containing a plurality of host interface units (I/O modules), disk drives, and disk interface units (disk adapters). The host systems access the storage device through a plurality of channels provided therewith. Host systems provide data and access control information through the channels to the storage device and the storage device provides data to the host systems also through the channels. The host systems do not address the disk drives of the storage device directly, but rather, access what appears to the host systems as a plurality of logical disk units. The logical disk units may or may not correspond to the actual disk drives. Allowing multiple host systems to access the single storage device unit allows the host systems to share data stored therein.
Mainframe computers are large scale computer system architectures that are used by large organizations for bulk data processing, such as financial transaction processing. Mainframe computers offer enhanced availability, scalability, reliability and security along with high volume data throughput, among other features. Input/Output (I/O) devices may be coupled to interact with mainframe computers that may include an I/O subsystem that communicates with the I/O devices over communication channels. The I/O subsystem controls data flow between I/O devices and main storage. The I/O subsystem may be coupled to the central processors of the main system and may communicate directly with the I/O devices. The I/O subsystem may communicate with the I/O devices using multiple types of interfaces, including, for example, communication channels such as Fibre channels. For example, IBM Corporation's System Z® is a mainframe platform and computing environment that is widely used in the industry and that includes z/Architecture-based systems and zSeries mainframes. System z components may operate with IBM's z/OS® (operating system) and/or other zSeries-compatible operating systems.
Fixed block architecture (FBA) is a disk layout in which each addressable block on disk is of the same size. In an FBA system, data (logical volumes) are mapped over the fixed-size blocks and a disk drive stores the data in the blocks of fixed size. Specifically, the FBA architecture has two characteristics: each physical block is the same size and each physical block is individually addressable by a value called the logical block address (LBA). In some cases, an FBA device may be characterized by tracks and cylinders and in which the physical disk may contain multiple blocks per track, and the cylinder may be the group of tracks that exists under the disk heads at one point in time without performing a seek operation. For further discussion of storage control using FBA, an/or other formats, to provide high-speed direct access storage for general purpose data storage and system residence, reference is made, for example, to IBM Corporation, “IBM 3880 Storage Control: Models 1, 2, 3, 4,” Description Manual, Pub. No. GA26-1661-9, Tenth Ed., September 1987, 446 pp., which is incorporated herein by reference.
Hosts may address FBA devices over a number of channel connections, including Fibre channel connections. For example, in a conventional system, a host may include an operating system and a Fibre Channel connection portion, which includes hardware and/or software for facilitating a FICON data connection between the host and a conventional data storage device. FICON (Fibre Connection) operates on a Fibre Channel protocol from IBM Corporation and may be used in connection with implementing Fibre channel connections to provide high-speed connectivity between a channel and a device and allows multiple data exchanges in full duplex mode. FICON is compatible with z/Architecture computing systems in connection with I/O devices performing I/O processing therewith. For a discussion of features and implementations of FICON systems and suitable Fibre channel protocols operating therewith on z/Architecture computing systems, reference is made to J. Entwistle, “IBM System z10 FICON Express8 FCP Channel Performance Report,” Technical paper, August 2009, 27 pp., which is incorporated herein by reference.
One known system that enables FICON device access of FBA storage devices is IBM Corporation's z/OS Distributed Data Backup (zDDB) system as implemented in IBM's DS8000® product, and reference is made, for example, to B. Dufrasne et al., “IBM System Storage DS8000: z/OS Distributed Data Backup,” IBM Corporation, Redpaper REDP-4701-00, Nov. 16, 2010, 16 pp., which is incorporated herein by reference. However, with this system, there is an architectural storage device size limit of two (2) terabytes (TB). Specifically, for a 512-byte block (9 bits) and a 4 byte LBA offset, only 2 TB (32 bits plus 9 bits=41 bits or 2 TB) of a FICON-connected device may be accessed.
Accordingly, it would be desirable to provide improved software and hardware that eliminates or reduces the issues noted above, such as by enabling large FBA device support over FICON connections.